This invention relates to a deaerator tray and tray assembly for a steam boiler feedwater heater system. Deaerator systems are well known in the art and are used for removable of corrosion causing gases such as oxygen and carbon dioxide that are dissolved within the feedwater of steam systems. An example of such system is described and illustrated in U.S. Pat. No. 4,759,315 such disclosure being incorporated herein by this reference thereto. In that patent there is illustrated in FIG. 5 a prior art deaerator tray assembly using rectangular troughs in the form of trays having a flat bottom and vertical side walls. The trays are elongated and are stacked in a staggered and spaced relation. It has been found that some of the feedwater overflowing from the upper trays down through the stack adheres due to surface tension to the underside of the bottoms of the troughs and drops from the latter near the center which results in water by-passing the underlying trays. For example, due to the effect of surface tension some of the water from the trays in the first horizontal row will miss the trays in the second horizontal row and will cascade directly into the trays in the third horizontal row. This water is said to "by-pass" the trays. As the steam from below rises up, it will try to flow across the water which is cascading down from tray to tray. When the water by-passes the trays, steam will miss that amount of water and this will result in poor heat transfer, decreasing the efficiency of the tray system.
In the process of deaeration, in order to obtain maximum heat transfer, steam must be intimately mixed with the water which must be distributed in the form of uniform thin film. In current technology, water is allowed to cascade down through several rows of trays. Steam is fed from below and when the steam comes in contact with the water, which is cascading in the form of a curtain, heat transfer takes place. The efficiency of the heat transfer greatly depends on two factors, namely surface tension in the water and consequently water by-passing the trays below.
Various tray geometry has been utilized to overcome the problem of surface tension and the resulting by-passing of the water thereby reducing the efficiency of heat transfer. As pointed out above, the prior art has utilized rectangular shaped trays or troughs. The prior art has also used a tray geometry where the bottoms of the trays are flat and the side walls vertical but the side walls make a small curve with respect to the bottom. This small curve or bend assists the water in traveling easily to the underside of the tray and thus increases the tendency for the water to by pass the lower trays. In an attempt to overcome this problem V-shaped troughs or trays have been utilized and as pointed out in the aforesaid U.S. Pat. No. 4,759,315 the V-shaped troughs have been provided with downwardly and outwardly inclined wing-like guide structure connected to the upper weir edges of the troughs. The lower edges of the guide structure are notched, presenting a plurality of liquid guiding extensions. While this configuration for the deaerator tray structure has represented an improvement over the prior art it has still left something to be desired.